Tag Archives: gpio

Measuring a pulse duration in a pulse train was my last week headache with the TD1208 and the not so well documented EFM32. Basically, my objective was to activate a timer on a pulse train to measure the duration of the pulse. This duration was measured about 100uS and occurred at 1 Hz.

My choice was to rise an interrupt on each signal front (raising and falling) and measure the duration between the two first interrupt call. Some reset function ensure we are measuring the low state duration (100uS) not the high state duration (1s). This part will not be described here. The purpose of this post is to describe the main hole I fallen in.

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Recently I killed on of SigFox Td1208 device by misprogramming it, destroying the bootloader. In a such situation serial port is not anymore accessible for programming. The use of JTAG port is a necessity. On the TD1208, jtag has been repaced by SWD which is a 2 wires port doing the same thing.

To use this port, you generally need a specific interface. These interfaces like Jlink are expensive (> 300€), some are less like BusPirate (30€). By the way, if you do not have it, you will have to order and wait for it. That’s why I’ve taken the choice of using my BeagleBone black device GPIO to pilot these signal. This code can easily be port to RaspberryPI…

Some new hacking on Raspberry PI, the objective is to get a TC74A5 3.3VAT temperature sensor working with a RPI. This sensor is a digital sensor type 2 wires I2C operating at 3.3V with a precision of 2°C.